Types of Radioactive Decay to Know for Intro to Applied Nuclear Physics

Radioactive decay is a natural process where unstable atomic nuclei transform into more stable forms. Understanding the different types of decay—like alpha, beta, and gamma—helps us grasp how elements change and release energy, which is crucial in applied nuclear physics.

1. Alpha decay

   • Involves the emission of an alpha particle, which consists of 2 protons and 2 neutrons (helium nucleus).
   • Results in a decrease of the atomic number by 2 and the mass number by 4.
   • Common in heavy elements like uranium and radium, leading to more stable isotopes.
   • Alpha particles have low penetration power; they can be stopped by a sheet of paper or skin.
   • Often accompanied by gamma radiation as the nucleus transitions to a lower energy state.

2. Beta decay (β- decay)

   • Involves the conversion of a neutron into a proton, emitting an electron (beta particle) and an antineutrino.
   • Increases the atomic number by 1 while the mass number remains unchanged.
   • Common in neutron-rich isotopes, helping them achieve stability.
   • Beta particles have greater penetration power than alpha particles but can be stopped by plastic or glass.
   • Can lead to the emission of gamma rays as the daughter nucleus transitions to a lower energy state.

3. Positron emission (β+ decay)

   • Involves the conversion of a proton into a neutron, emitting a positron (the antimatter counterpart of an electron) and a neutrino.
   • Decreases the atomic number by 1 while the mass number remains unchanged.
   • Common in proton-rich isotopes, facilitating their path to stability.
   • Positrons can annihilate with electrons, producing gamma radiation.
   • Similar penetration power to beta particles, requiring denser materials for shielding.

4. Electron capture

   • A process where an electron from the innermost shell is captured by the nucleus, combining with a proton to form a neutron and emitting a neutrino.
   • Decreases the atomic number by 1 while the mass number remains unchanged.
   • Often occurs in proton-rich isotopes that seek stability.
   • Can result in the emission of characteristic X-rays as electrons fill the vacancy left by the captured electron.
   • Typically occurs in conjunction with gamma decay as the nucleus transitions to a lower energy state.

5. Gamma decay

   • Involves the emission of gamma rays, which are high-energy photons, from an excited nucleus.
   • Does not change the atomic or mass number; it is a form of energy release.
   • Often follows other types of decay (like alpha or beta) as the nucleus moves to a lower energy state.
   • Gamma rays have high penetration power and require dense materials like lead or several centimeters of concrete for shielding.
   • Plays a crucial role in the stability of the nucleus by dissipating excess energy.

6. Neutron emission

   • Involves the release of one or more neutrons from an unstable nucleus.
   • Can occur in heavy elements or during certain nuclear reactions, such as fission.
   • Does not change the atomic number but decreases the mass number by the number of neutrons emitted.
   • Neutrons are uncharged and have high penetration power, making them difficult to shield against.
   • Often associated with the production of secondary radiation, such as gamma rays.

7. Proton emission

   • Involves the release of a proton from an unstable nucleus.
   • Decreases the atomic number by 1 and the mass number by 1.
   • Typically occurs in very heavy or proton-rich isotopes that are seeking stability.
   • Proton emission is less common than other decay types and requires significant energy.
   • The emitted protons can lead to further reactions, including secondary decay processes.

8. Spontaneous fission

   • A process where a heavy nucleus splits into two or more smaller nuclei, along with the release of neutrons and energy.
   • Typically occurs in very heavy elements like uranium-235 and plutonium-239.
   • Results in a significant decrease in mass number and can produce a variety of fission products.
   • Releases a large amount of energy, making it a key process in nuclear reactors and weapons.
   • Can lead to a chain reaction if the emitted neutrons induce further fission in nearby nuclei.